Bryant-Greene said the changes were significant, and "happening quite quietly". It was "a first step towards pushing the eftpos system towards the credit network".

"Effectively what it means is that as we start paying that fee more, our prices have to go up. And that's going to be the case across the industry."

New Zealand Retailers Association chief executive John Albertson said there was "no justification for that higher fee".

"Our position on it at this point is that we like the technology, which is very modern and sexy, but we don't like the fee structure."

Massey University Centre for Banking Studies director David Tripe said processing payWave on the credit network "could change the whole economics of eftpos quite significantly and quite quickly".

"Visa and MasterCard could bypass the standard eftpos-processing system - meaning the Paymark system, which has allowed for very low cost eftpos transactions, could be undermined," he said.

"One of the risks that arises from this is that eftpos as a whole may go from being this effectively free and very cheap service, to one that moves under the control of Visa and MasterCard and therefore becomes a whole lot more expensive."

Tripe said the consequences of such a shift were hard to predict, but it was an "alarming" prospect.

He said he had spoken to disgruntled retailers about the fees, and higher fees could mean retailers raised prices, discouraged use of eftpos or introduced charges for eftpos transactions.

For banks gaining the fees, he said, there was "certainly a short-term gain".

In December, Visa was processing more than 1 million payWave transactions a month.

For retailers being charged for these transactions at the same rate as credit cards, this could mean millions in additional bank fees.

Visa country manager for New Zealand Caroline Ada said usage of the cards more than doubled in the last six months of 2013.

Eftpos Canterbury owner Steve Batey said the company was in the process of phasing out old eftpos machines, and new machines would be equipped with payWave, unless businesses specifically opted for an older system.

Batey was aware of the changes to fees, and said banks were "pushing the new debit cards". He said banks had made no money on eftpos cards, and the "tap and go" fees allowed them to recoup costs.

Batey said machines five years or older would all be phased out by June 2014.

Alberton said that, for retailers, advantages of payWave were "a perception thing rather than a reality".

"If you look at it in terms of absolute time saved at the checkout - it's probably minimal. There's not a huge time saving."

Z service stations are the largest adopter of payWave in New Zealand. A spokeswoman said the company would "always consider cost versus benefit when we're making business decisions, and given our focus on speed and service for customers, we believe payWave is worth the investment".

Foodstuffs South Island finance manager Malcolm Wratt said anything which could potentially lead to higher costs for its owner-operators was a concern.

The chain was deciding whether to implement payWave, and "one of the factors that will come into this consideration will be the cost of the service", he said.

Representatives from Kiwibank, ANZ, ASB and BNZ said merchants could request their fee plans be reviewed if they felt they were being overcharged. Fairfax NZ